The first Chrysler “Hemi” V8 engines appeared on the market in 1951. Since that time, said “Hemi” engines have been used extensively in the custom car field, being modified and swapped into countless custom vehicles, and in racing form, achieving dominance in several forms of motor racing.
The contemporary implementation of the Chrysler “Hemi” V8 engine first appeared on the market in 2003, in the 5.7 liter version. Since that time, Chrysler Corp.
has produced other versions, including 6.1 liter and 6.4 liter engines. The fuel delivery and spark delivery systems on the contemporary versions of the “Hemi”, like all contemporary automotive engines, are controlled by a dedicated purpose computer, known as an Engine Control Unit, or ECU.
During the 2009 production run, Chrysler Corporation improved their 5.7 Liter Hemi Engines with regard to better fuel economy and reduced emissions performance by the installation of a Variable Camshaft Timing (VCT) system and a Displacement-on-Demand (DOD) system in those engines. Under the control of an upgraded ECU, the VCT system changes the angular position of the camshaft with respect to the crankshaft as a function of the power being requested from the engine (driver's gas pedal position) and engine revolutions per minute (RPM). With VCT, the engine system can provide lower emissions and greater economy in response to real time conditions.
The DOD system deactivates half of the engine's cylinders (alternate cylinders in the firing order) under conditions of low power demand, which reduces engine pumping losses under conditions of high manifold vacuum, thereby providing significant increases in fuel economy and reductions in emissions-per-mile.
There is an expanding demand for late model Chrysler Hemi engines in the custom car, aftermarket and high-performance automobile construction fields. In many of those projects, the customer wants the engine to be modified to produce significantly greater power than does the stock engine.
One of the essential modifications along the path to greater engine power is the replacement of the conservative factory camshaft with a “performance” camshaft that opens and closes the valves faster than the stock camshaft, opens and closes the valves at different points in the operating cycle than does the stock camshaft, and lifts the valves higher than does the stock camshaft.
Unfortunately, the VCT and DOD systems preclude the replacement of the stock factory camshaft with a performance camshaft. There are two reasons for that limitation.
First, the effective range of camshaft position adjustment which the VCT system provides would guarantee that, as a result of the higher valve lift values that performance camshafts attain, all the valves would collide with the pistons at the extremes of VCT adjustment travel. That would cause immediate, severe engine damage and probable engine destruction.
Secondly, performance camshafts impose acceleration rates on the cam followers that are substantially greater that those embodied in the stock camshaft. That causes much higher axial forces to be imposed on the DOD-style cam followers at high engine speeds, and those higher forces overpower the DOD cam followers' ability to remain in the non-collapsed (active) position, causing the DOD cylinders to unintentionally deactivate at high power-high rpm operation.
It is therefore an object of the present invention to provide the ability to install a performance camshaft in the new VCT-style Hemi engines by means of replacing the VCT and DOD components with suitable alternatives.